The present invention relates generally to combine harvesters and, more particularly, to a rotary cleaning mechanism in combines for cleaning unwanted residue, such as chaff, straw, etc., from threshed grain.
Conventional cleaning systems clean threshed grain by blowing air through a set of planar sieves utilizing gravitational forces to urge cleaned grain through the sieve openings. With the advent of higher capacity threshing and separating mechanisms, such as rotary axial flow combines, the capacity for threshing grain has increased beyond the capacity of conventional cleaning systems to clean the grain. Accordingly, it is desirable to increase both the capacity and the efficiency of cleaning systems in combine harvesters so as not to limit the throughput capability of the combine.
Prior art rotary cleaning devices provide mechanisms for reciprocatably moving the entire sieve, extending 360 degrees around the axis of rotation, in a fore-and-aft direction. To counterbalance the vibrations induced by the moving of this great amount of mass, of second sieve was reciprocated in the opposing direction. Moving these great amounts of mass at one time requires massive drives and supporting components. Accordingly, it would be desirable to provide an oscillating mechanism that would individually move sections of the cleaning sieves along a reciprocatory path, although maintaining the counterbalancing effect by keeping the mass moving forwardly substantially equal to the mass moving rearwardly at any given point in time.